Return the number of parameters in a model expression.

The get_num_par function returns the number of parameters, both frozen and thawed, in the model assigned to a data set.

Parameters:id (int or str, optional) – The data set containing the model expression. If not given then the default identifier is used, as returned by get_default_id.
Returns:npar – The number of parameters in the model expression. This sums up all the parameters of the components in the expression, and includes both frozen and thawed components.
Return type:int
Raises:sherpa.utils.err.IdentifierErr – If no model expression has been set for the data set (with set_model or set_source).

See also

Return the number of frozen parameters.
Return the number of thawed parameters.
Set the source model expression for a data set.


Return the total number of parameters for the default data set:

>>> print(get_num_par())

Find the number of parameters for the model associated with the data set called “jet”:

>>> njet = get_num_par('jet')